"Plastic steps" error disappears. Why?

We have an issue where a complex SQL caused the error "Insufficient memory for Plastic Steps for this request". While testing the affects of the NOVIEWFOLD diagnostic, it was found that the error no longer shows. Now the error cannot be reproduced, even with the diagnostic off. According to the DBA, no database configurations have been changed since the issue arose.

The question at hand is: "what can make the error no longer appear with the same SQL and same configuration?".